1. Field of the Disclosure
Embodiments of the present invention relate to a touch panel, and more particularly, to an apparatus for driving of touch panel capable of implementing a haptic function.
2. Discussion of the Related Art
A touch panel is a type of input device that is included in image displaying devices such as Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Plasma Display Panel (PDPs), Electroluminescent Displays (ELDs), Electrophoretic Display (EPDs), and Organic Light Emitting Devices (OLEDs), and allows a user to input information by pressing or touching a touch sensor of a screen with a finger, a pen or the like while a user looks at the screen of the image displaying device.
Recently, the touch panel is widely used for an input device of portable information devices such as smart phone and table PC, and also used for an input device of electronic equipment such as computer monitor, monitor and television.
According to a touch sensing method, the touch panel may be classified into a resistive type, a capacitance type, and an infrared sensing type. The capacitance touch panel has attracted great attentions owing to advantages of easy manufacturing method and good sensitivity. The capacitance touch panel may be classified into a mutual capacitance type and a self capacitance type. In comparison to the self capacitance type touch panel, the mutual capacitance type touch panel is advantageous in that it enables a multi-touch input.
In case of a general touch panel, a touch point may be sensed by the use of finger or pen. However, it is difficult to sense a touch force, that is, touch pressure. Accordingly, US Patent Application Publication Number 2014/0062933 published on Mar. 6, 2015 (hereinafter, referred to as “'933 Patent Document”) discloses a capacitance touch panel which senses both touch force and touch point.
As shown in FIG. 1, in case of the capacitance touch panel disclosed in the '933 Patent Document, a touch force is sensed by a change of capacitance (Cm1) in accordance with the decrease of distance in between a pair of force sensing electrodes 12 and 22 being overlapped with each other and being parallel to each other, and a touch point is sensed by a change of capacitance (Cm2) in accordance with a fringe field in between a pair of point sensing electrodes 14 and 24 being not overlapped with each other and crossing each other.
However, the capacitance touch panel disclosed in the '933 Patent Document has the following disadvantages.
First, the force sensing electrodes 12 and 22 for sensing the touch force are separated from the point sensing electrodes 14 and 24 for sensing the touch point so that it causes a complicated electrode structure. In addition, a touch resolution is lowered due to the point sensing electrodes 14 and 24 crossing each other.
Also, efficiency of sensing the touch force is proportional to an area of the force sensing electrodes 12 and 22 facing each other. Thus, if the force sensing electrodes 12 and 22 are decreased in size so as to improve the touch resolution, the efficiency of sensing the touch force is lowered.
In order to improve the touch resolution, if the point sensing electrodes 14 and 24 are overlapped with each other, the capacitance (Cm2) formed between the point sensing electrodes 14 and 24 is maintained at a constant value without regard to a touch of conductive object, whereby the efficiency of sensing the touch point is lowered.
Meanwhile, some of image display devices including touch panels support a haptic function. The haptic function may provide the sense of touch to a user through haptic effects of changing a frictional coefficient to be sensed on a touch screen by a user. The image displaying device with the haptic function, which is the device for providing the sense of touch to a user, may include one or more haptic output device, for example, actuator. Thus, the image displaying device with the haptic function includes the additional actuator for the haptic function, whereby a structure of the device is complicated and a cost of the device is also increased.